Variable Interest Entities (Sales and Cash Flows)(Details) (Cinergy Receivables [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 514	$ 518	$ 1,664	$ 1,618
Gain (loss) recognized on sale	(3)	(3)	(9)	(10)
Cash proceeds from receivables sold	518	531	1,674	1,651
Return received on retained interests	1	1	4	4
Collection fees received			1	1
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	765	711	2,214	2,118
Gain (loss) recognized on sale	(2)	(3)	(8)	(9)
Cash proceeds from receivables sold	758	733	2,204	2,130
Return received on retained interests	2	2	5	5
Collection fees received			$ 1	$ 1